The present invention relates generally to an apparatus for shrinking or radial compression forming of metal workpieces, and more particularly to improved shrink forming apparatus for maintaining accurate alignment of the workpiece with respect to its desired center or axis.
Shrink forming apparatus are utilized to decrease the exterior diameter of an annular workpiece. One use of such shrink forming apparatus is to ensure the roundness of assembled vehicular wheels. One type of such wheel rounding shrink forming apparatus or machine is disclosed in Luedi et al., U.S. Pat. No. 3,461,710, and the disclosure therein is incorporated herein by reference.
For vehicular wheels it is essential to insure perfect roundness of the wheel rim and accurate alignment of the rim with respect to the axis of rotation of the wheel. Conventional shrink forming machines include rounding dies that engage the rim of the wheel for rounding the rim and boring tools for accurately locating and forming openings in the wheel spider. It is these openings which determine the axis of rotation of the wheel.
The continuing demands of the vehicle manufacturers for accuracy creates a necessity for achieving the highest possible levels of accuracy in the wheel making art. True roundness of the wheel rim, while highly desirable, is ineffectual unless the entire rim is accurately aligned with respect to the axis of rotation of the wheel by the wheel rounding dies. The axis of the rotation of the wheel is typically defined by a boring spindle which creates either a central hub opening in the wheel center that coacts with an associated portion of the vehicle, or attachment bolt holes that are accurately located within the wheel center. Although the invention is described in connection with a wheel-forming machine, it is fully applicable to machines for forming other types of workpieces.
Prior known shrink forming machines have attempted to provide the desired roundness and alignment by controlling the radial movement of the wheel rounding dies. The movement of these dies is governed by an outer pressure ring or shrinker barrel whose axial travel is controlled by a series of cylindrical guides. A minor clearance along the guide path of the shrinker barrel therefore can cause misalignment and an out-of-roundness condition of the workpiece.
It is therefore one object of this invention to provide an improved shrink forming apparatus that provides positive location of the outer shrinker barrel in its forming position and thereby insures accurate alignment of the machine parts and a very accurately formed workpiece.
It is a further object of this invention to provide a guiding mechanism for the outer shrinker barrel of a shrink forming apparatus that will not be subject to increasing clearances as the components wear through usage which otherwise would reduce the accuracy of the workpiece being formed.
Additional objects and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.